34.2mpg + 424whp = FTW

Update:

I have been on the road a lot lately doing some tuning trips which has given me ample time to dive into the inner workings of the 08sti's ecu. By datalogging and recalibrating over and over the timing, fuel, and the cams I have been able to extract some wicked MPG with my new setup. All the while keeping the smooth driveablity and max power the same. So now there is no need to load an economy map since its all tuned on one.

Between the awesome Deatschwerks Injectors, AMS Turbo kit, and some really good tuning I can proudly say I have achieved the perfect setup. Not only is the car nice and quiet like stock, gets amazing gas mileage, it also makes a ton of power.

How perfect you say? How about for this last tank of gas I have driven 210 miles and avg 34.2mpg :banana: and still make over 420whp.

Who says you can't have your cake and eat it too..

 

Highway, right?

 

No actually this is about 90% city driving. I have only left alpharetta once and that was to drive to buckhead. So figure 35miles of the 210 has been on GA400.

Actually if you take the distance and divide it by the time it gives me an avg speed of about 37mph... so hardly highway miles.

 

What the hell? ...nice.

 

nice job, keep up the good work

 

Sick

 

so you are making the 420 whp on the same settings that yield you 34 mpg?

 

Yes sir :bowdown:

 

Its just hard to believe, you're making me want to get a new sti and make you tune it.

 

:eek3::eek3:

Everyone I talk too thinks I am a freak to get 23mpg average out of my stock 08 STI.

Could you, in theory, do this with a otherwise stock car? Modify a stage 1 map to get stage 1 power and uber-MPG's?

 

No

 

Well, that stinks. I assume its mod combo you have on that car. You car makes more power than I would ever want. :wiggle:

 

That's pretty cool. Not a lot of people can say they get 30+ mpg out of their 400+hp car...

 

Were you able to re-scale the nav system for the larger injectors? My spec b (same nav setup) reads consistently in the high 30's ~355whp because it doesn't know about the 850cc injectors/larger fuel pump.

 

Your turbo has to push harder to get your car going. That GT35r can just snort and the STi is moving.

 

You would have to give more gas tot get the bigger turbo to spin though.

Im with the above post, maybe the Navi doesn't really know how much gas is going in. Ie 10% of 850 > 10% of 600

 

You'd be surprised at how much easier that GT35r spools. 2psi of GT35r is like 10 psi of the VF.

 

Plus what you guys are failing to realize is that the 35R takes a little longer to spool. So while your stock turbos are spooled constantly shifting thru gears in traffic, dougs just driving a 2.5rs with AVCS and a great tune where I'm sure the mixture is slightly leaner in the low rpms where the fuel isn't needed as much. Advantage = Doug

 

While STILL making more power down low.

 

How can you make more power without more fuel without being really lean?

 

hmm, good question

 

It's not always about fuel. It's ALL about efficiency.

 

Thats true, but the internals are exactly the same., the engine uses fuel and air in the same way..
So in order to get more power why wouldn't you have to add more fuel and air?

When Scott tuned me said i would get better millage. And i did, in the city, when you step on it ( you are making alot more power and using more fuel) it would be less.

 

You just answered your own question. Doug's isn't pushing it. He's scooting around town. That 35r is pushing a lot more air with very little effort hence it's efficient. Plus the air is much cooler so the car likes it.

 

Yes, i believe that. Though 34 seems a bit excessive... Back to the original question... Is the navi re calibrated ?

 

The larger turbo and hotside allows the engine to breath making it more efficient off boost. More efficient also means the car makes more off boost hp then stock. So accelerating the car from a stop without having to get into boost becomes easier thus using less fuel.

I am now able to drive the car around pulling off from stops and accelerating up to 40-50mph quickly without ever going over 2-3psi... thats how I can get such good mpg.

Oh and Navi reads off the front O2, Map, and vehicle speed and then calc mpg. Everytime I have used it and then filled up at the gas station its been within 1-2mpg.

 

Or a better example would be if you took an NA only car. Now take that NA car and run it through a 1.5" catback exhaust (think stock VF turbo), now if you changed it to a free flowing 2.5" (tial hotside) cat-back exhaust you would pick up MPG as the engine becomes more efficient even in pure NA form.

This example is even more pronounced with a turbo car because I am able to accelerate the car quickly now using only NA power vs having a turbo that spools instantly but chokes off the NA power.

 

Oh and Navi reads off the front O2, Map, and vehicle speed

O2 would tell it the FAR right?

Map would tell it % of Injectors being used

and speed is...well speed

how does it adjust for the bigger fuel injectors?

 

Also the with the Dual AVCS I am able to play with valve overlap allowing me to make more power off boost. That with the fact that I can now maintain a leaner afr for longer since the car doesn't need the boost now to accelerate it from a light.

 

Actually thinking about it now the NAVI doesn't calc fuel economy. The ecu does, so when I rescale the injectors in the ecu it is re calibrated.

Had a blonde moment I guess.

 

This is prob a really stupid question.
Dont you just say that instead of using 50% ECU at 6000rpm use 40% leaving to a false seance of higher mileage?

 

Dual AVCS = more Dynamic Compression Ratio

People fail to realize that when you change the intake and exhaust cam advance you are changing how much compression is being bled off at low RPM. Cam overlap has a lot to do with how high compression NA cars can still operate even on pump gas. Years ago people thought that 12 to 1 compression meant running pump gas was impossible but now there are stock cars approaching that range.

 

PS. i appreciate you taking the time to answer all these stupid questions.

 

I think the part that the navi uses is just inj % - which means that no matter what you scale it to - it just sees xx% injector and calculates that - I don't think the mpg is reading accurately - I know it didn't in my car, it was pretty easy to get over 40mpg on the display, but it was really in the 20's judging by the mileage vs. gas I was putting into the car.

The best way to test it would be to fill up the car, drive it for xx(x) miles, more being better - and then bringing it back to full again seeing how much you put in...gallons/x(miles) = mpg

 

Dude Doug just stated that it's always within spec with his calculated spec at the tank.

 

At least in stock trim, the one on my dash is usually +/- 1 mpg from my calculations. Usually it is actually pessimistic and gives me a reading that is less than my calculations.

 

Very nice Doug! now I just have to hit the lotto and have you build mine...I want to hear a bit more rumble than yours though

and yes in stock trim my Average MPH is within 1mpg of my calcs. As longfury said it is generally lower than my calc.

 

I think it honestly had a lot to do with that half tank of 93 came from my gas tank (shameless input)

 

Why did I buy a tiny Honda again? :unamused:

 

Man! If only you could get those numbers out of a good looking subaru!

 

because 'it handles better than a wrx' :rofl:

 

I get that it USED to be very close to what was on the display, mine was too - but as soon as the new injectors went in - my mpg went through the roof.

To be clear - I don't doubt that you can get 34mpg on a big turbo'd subie - I'm questioning whether or not the nav display is accurate - and if it is, how did you do it, because I'd like mine to display correctly as well.

 

^^^ Lucky... I get 19.. 20 on a good tank.

 

18mpg:unamused: ...filled up yesterday

 

Doug, just out of curiousity, is it possible to make these EMS modifications to my 04 w/ the GT35r/ hydra?

-Chandler

 

I am in the same boat. Mine still says I get 30+ MPG but after doing the math, there is no way I am. 14 gallons of gas and only going 250 miles does not equal 34mpg. Not doubting your tuning skills I just want to know how you made the trip computer accurate.

 

What part of Doug NOT doing anything to the trip computer do you guys not understand.

He has stated in the Nasioc thread that it's not 100% accurate. He went to Florida and It said 30+ again but when he calculated it with mileage vs amount of fuel consumed he got 27 mpg.

Regardless 27 mpg on a 400+ hp car is impressive when the stock STi's are barely cracking 20 mpg.

 

Again, that is my point...my computer says I get 30+ MPG all day long but I know it is NOT accurate. If he is claiming 34 MPG then I believe him and want to know how he got his trip computer to be accurate if that is how he is calculating 34 mpg. Now, if he said he was getting 450 miles to the tank, then I wouldn't have even said anything about his trip computer.

Again, I don't doubt Doug for a second...If he says something about a subie, I listen. Unlike some of the other people on these boards.

I don't follow any threads on NASIOC so how in the fawk am I suppose to know what he said on there?